Conventionally, there is known a technique for transmitting video data displayed by an arbitrary communication device to another communication device by wired or wireless connection, and for displaying the video data received by the other communication device.
In a conventionally-used screen-data-transferring technique, a communication device at a transmitter side and a communication device at a receiver side are connected to each other on one-to-one basis, and the communication device at the transmitter side transmits video data by unicast. Therefore, the case in which a plurality of communication devices are connected at the receiver side has not been considered. In such case, if video data is transmitted to the plurality of communication devices, the video data is transmitted to each one of the communication devices by unicast, thereby increasing processing load.